1. There is no sun, which means no shadows, etc.;2. There is nothing in the surrounding environment, so it feels like you are on a floating platform in the sky.

Point 1 should be easy to fix, and I would recommend uploading it to add-ons after that. Point 2 will probably be harder to fix and fixing it may or may not happen, so don't hold off uploading to add-ons because you have not fixed point 2.